By using a Notch2f/fE8I-Cre+ mouse model (lacking Notch2 expression in peripheral CD8+ T cells but not in CD4+ T cells), the authors found that the knocking out of Notch2 inhibited (compared to the control) the differentiation of naive CD8+ T cells into CTLs and could not control the growth of OVA-expressing EG7 thymoma cells and EG7 cells in vivo. The gene discussed is CD8A; the disease is thymoma.